1. Field of the Invention
The present invention relates to a tower suitable in particular for a wind energy turbine. More specifically, the present invention relates to a hybrid tower including a tower segment comprising concrete material and at least one other tower segment comprising steel. In particular, the present invention is related to the connection between the concrete tower segment and the steel tower segment.
2. Related Prior Art
Towers for supporting diverse elements are well known and used in different technical fields. For example, tubular towers are used to support the nacelle of a wind energy turbine wherein the nacelle is rotatably mounted on top of the tower.
In order to comply with the increasing demand for using regenerative energy resources for electrical power distribution networks, modern wind energy turbines increasing require greater power generation capacity. Further, increasing rotor diameter size of wind energy turbines requires increasing heights of the towers.
Up to a certain height, towers for wind energy turbines can be made from tubular segments of steel. The tubular segments can be cylindrical or conical, or a combination of both types of tubular tower segments can be used.
In order to be able to use tubular tower segments made of steel for relatively high towers, it is known to employ at the base or lower portion of the tower a tubular tower segment made of reinforced concrete. There are basically two known designs for connecting a tubular steel segment to a tubular concrete segment.
One alternative for such a connection is shown. In FIG. 4. According to this design, a reinforced tubular concrete segment 1 having pre-stressing elements 2 connects to a flanged steel segment 3 at its upper end, the steel segment 3 also being tubular. Disposed between the concrete segment 1 and the steel segment 3, there is a gap 4, which needs to be sealed. It is difficult to seal the gap 4 because the dimensions of the gap are likely to fluctuate, particularly when the tower is subjected to radial loads.
Another known design for connecting a tubular steel tower segment to a tubular concrete tower segment is shown in FIG. 5 (in this figure, the same reference numerals as in FIG. 4 are used to refer to similar elements.) The concrete tower segment 1 of this design includes reinforcing elements 5 (reinforcement steel) without any pre-stressing elements. A lower portion of the steel tower segment 3 is embedded in the concrete of the concrete tower segment 1 and includes a flat ring-like anchoring element 6, which is also embedded in the concrete. An outer edge of the anchoring element 6 extends proximally toward an outer surface 7 of the concrete tower segment 1. It is common to observe a formation of cracks 9 due to significant concentration of tension forces within that area 8.
It is an object of the present invention to provide a hybrid tower comprising a tower segment made of concrete and a tower segment made of steel wherein the connection between the segments is improved.